The invention relates to a method of determining a direction of a drilling pattern. The invention further relates to a software product and a rock drilling rig. The field of the invention is disclosed in more detail in the preambles of the independent claims of the application.
Usually, tunnels are excavated according to a predetermined tunnel design. The tunnel design determines e.g. the tunnel line of a tunnel to be excavated in the project coordinate system of a tunnel worksite. Further, the tunnel design determines a coordinate system to be used in each case. Since a tunnel is excavated in rounds, a drilling pattern is designed in advance as office work for each round, the drilling pattern determining at least the number, locations, directions and lengths of holes to be drilled. The drilling pattern has a coordinate system of its own which is independent of the project coordinate system of the tunnel worksite. In order for the drilling to be performed, the location and direction of a rock drilling rig is to be determined with respect to the tunnel line and, further, it is necessary to be able to direct the drilling pattern for a new round so that the tunnel progresses in accordance with the designed tunnel line.
In practice, tunnel excavation proceeds such that when the preceding round has been drilled, charged and blasted, broken rock material is transported elsewhere, which is followed by the rock drilling rig being driven to the tunnel face, and navigation. In navigation, the direction of the rock drilling rig is connected with the project coordinate system by means of a tunnel laser whose direction, in turn, has been determined by means of two coordinate points in the project coordinate system, the beam of the tunnel laser passing through these points. Information on the location of the rock drilling rig on the tunnel line may be provided by an operator, e.g. by feeding what is called a peg number. Since the tunnel line is determined in a project coordinate system, since a local site coordinate system is used at the drilling site and, further, since the drilling pattern has its own coordinate system, the project coordinate system and the site coordinate system are to be transformed to the coordinate system of the drilling pattern by means of transformation matrices or the like known per se. Further, when the tunnel to be excavated is curved or when the tunnel laser and the tunnel line are not parallel, an intersection point of the tunnel laser and the drilling pattern as well as hole direction angles are to be calculated in the control unit of the rock drilling rig in connection with each round in order to be able to drill the holes according to the drilling pattern.
In a known curve calculation, the tunnel line is determined by means of a curve table which contains points and their coordinate information, spaced at predetermined distances from one another. The operator communicates the location of the rock drilling rig on the tunnel line, i.e. in practice its distance from the start point of the tunnel, to the control unit, whereafter curve table points nearest to the drilling site are selected, and local coordinate systems are positioned at these points such that the y-axis of each local coordinate system points towards the next point of the curve table. Next, the intersection points of the tunnel laser and the local coordinate systems positioned at the points of curve table are calculated. Further, the coordinates of the intersection point of the tunnel laser and a navigation plane positioned at the drilling site are calculated by interpolating them from the coordinates calculated at the points of the curve table. The coordinates of the intersection point of a plane following the navigation plane are also calculated by interpolating in a similar manner. Subsequently, u and v hole direction angles between the tunnel laser and the navigation plane may be calculated on the basis of the coordinates of the intersection points.
A disadvantage of the present curve calculation is insufficient accuracy. It has been observed that accuracy depends e.g. on the magnitude of an angle formed by the tunnel laser with the tunnel line. This is because large angle values result in mathematical angle errors. Further, accuracy is deteriorated by the fact that the calculation is connected with the distance between the points of the curve table. Additionally, present curve calculation is difficult to understand, which makes tunnel designing and drilling pattern designing more difficult.